This invention relates to a single lens reflex photographic camera of the automatic diaphragm control type and, more particularly, to apparatus for resetting such a camera after exposure.
In a photographic camera of automatic diaphragm control type in shutter speed priority mode, the exposure time is preset to a value at the operator's will and then automatic exposure control is effected by driving the diaphragm control mechanism so as to stop the diaphragm down to a value for the proper exposure based on said preset value of exposure time. Afterwards, it is required to reset the diaphragm to the initial position, upon completion of this operation.
In a photographic camera as the single lens reflex camera having its objective diaphragm usually maintained fully opened except during actual photographing so that the desired focussing with a shallow depth of focus can always be readily made through a bright field of view, the initial position to which the diaphragm should be reset corresponds to the fully open diaphragm of the individual objective mounted on the camera.
Further, in a photographic camera of automatic exposure control type which is, as previously mentioned, adapted to provide the proper exposure by stopping down operation of the objective diaphragm based on the preset value of the exposure time, i.e., in the mode of so-called shutter speed adjustment priority, the stopping down operation for the proper exposure must have already been accomplished immediately before the shutter operates, the diaphragm value regulated as a result of such stopping down must be maintained during the exposure effected by said shutter operation, and the reset of the diaphragm to its initial position after completion of photographing must be done after completion of the shutter operation. In order that such a fundamental sequence of operations may be correctly done in the single lens reflex camera, not only is it necessary to incorporate up-and-down movement of the mirror which is peculiar to the single lens reflex camera into said sequential operation, but also it is required, especially for a camera provided with a focal plane shutter, which is used for lens interchangeability, that the diaphragm should have been stopped down to the value corresponding to the proper exposure at least before the leading shutter curtain starts and that the signal generated at the end of the trailing curtain's travel releases the diaphragm stop down mechanism so that the diaphragm, being biased to return to its initial position, can be actually reset to said initial position.
The present invention makes the operation to reset the diaphragm control mechanism more reliable and thereby meets the above-mentioned requirements.